Method of operating two-cycle internal-combustion engines employing liquid fuel.



r H. JUNK'ERS. METHOD OF OPERATING TWO CYCLE INTERNAL COMBUSTION ENGINES EM PLOYING LIQUID FUEL. APPLIOATION FILED AUG. 28, 1908.

1,1 17,498, Patented Nov. 17, 1914.

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HUGO JUNIKERS, OF AIX-LA-CHAPELLE, GERMANY.

METHOD OFOPERATING TWO-CYCLE INTERNAL-QOMBUSTION ENGINES EMPLOYING r LIQUID FUEL.

' Specification 6: Letters Patent.

Patented Nov. 17, 1914.

Application filed-August 28, 1908. Serial Np; 450,7 76.

have invented .a certain new and useful Method ,pf Operating Two-Cycle Internal- Combustion Engines Employing Liquid Fuel; and I do hereby declare thefoll'owing to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it pertains to Y make and use the same.

' combustion.

I My present invention relates to two-cycle internal combustion engines employing liquid fuel, introduced during and after passing the inner dead point, and more particu-v first few slow, revolutions The attempt to larly to the process of operating same.

The object of my invention is, to obviate the drawbacks of the processesof this kind lmown at present, among others the so-called Diesel process. I In the operation of internal combustion engines according to the known processes (equal pressure processes, Diesel process, or the like), whereby the fuel is introduced during-"the dead point position and at the beginning of the working stroke, and to which processes I shall refer in the following as to the so-called equal pressure processes, it is of the greatest importance :('1) That the compressed air of combustion is sufliciently heated after the close of the com pression to ignite the fuel, introduced at the beginning of the working'stroke. (2) That the introduced fuel should as far as possible be surrounded by the air of combustion, in

order that each particle of the fuel will find the air necessary for its combustion. .(3) That the impact ofthe fuel particles with.

the cool surfacesof the working chamber shall as far as possible be prevented, because the particles of fuel which adhere to these surfaces cannot take part in the process of compression the presence of the highly cooled wall surfaces of the compression chamber shall as far as possible be avoided, since these cool surfaces not only diminish the thermio elliciency, but also render the combustion of fuels of high boiling points difficult.

The engines hitherto employed for putting the so-called equal pressure process into practice are built as singlepiston engines, wherein the working piston operates within (4) That near the close of" a cylinder the end of which is closed by a cylinder head accommodating the necessary valves This head must, on account of the valves, be cooled just as much as thecylinder walls, so that by these engines more than one-halfof the walls of the dead space is cooled. The necessity of cooling the cylinder head and the arrangement of the valves in the head necessitate that on theone hand the cover becomes a very complicated casting, which when made for large engines is not reliable and renders the building of very large engines very diflicultand expensive, and that on the other hand the cooling is a drawback to the quick starting of the engine, since through this cooling the .air of combustion is cooled too much during the remove these drawbacks by. an initial .heatmg of the arr of combustion must be considered as an'unfavorable solution as far as the working of the. engine is concerned, since the 7 whole cycle of operations-takes place at higher: temperatures than necessary, and the drawn in mixture of air or an equivalent of noncombustible gas is diminished. Besides this the shape ofthe dead space in the i single-piston engines, which work according to the'so-called equal pressure process or they like, is veryiunfavorable, since in them the fuel must be either introduced sidewise or injected through the cylinder cover and drawn against the "piston, The lateral introduction of the fuel shows the drawback, that it takesplace during the whole time of injection in close proximity tothe cylinder cover, so that the main bodyof fuel comes into contact with fresh air of combustion at one side only. In a similar manner the injection of the fuel through the cylinder cover, whereby the fuel is drawn against the piston, shows drawbacks and is not suited at all for the combustion of oils which have high boiling points, particularly not at the start of the engine when the piston is still cold. According to my present invention these drawbacks are obviated, by executing the known so called equal pressure process in a two-cycle engine with two coaxially arranged and opposedly working pistons in which engine the dead space is not subdivided by projections or protuberances, nor by any recesses. To attain the end in view, the injection of the liquid fuel into the dead space formed between the working pistons .the aid of an engine with two pistons, the

comparatively long stroke of the engine in connection with the small diameters of the pistons and the favorable surface proportions thereby gained, offer exceptionally I great advantages, since atthe beginning of the in-stroke the surfaces are much larger than under the same conditions in a singlepiston engine, for which reason thegases are initially favorably cooled, whereas at the close ofthe compression the dead space principally consists of the end walls of the two pistons, which insmall engines need not be cooled at all and in the larger engines only very little, so that the withdrawal of heat near the close of the period of compression is exceedingly small. The double-piston explosion engines show under the same conditions this drawback, that a high compression is rendered difficult on account of the danger ever present in a too early ignition, which is impossible in a double-piston equal pressure engine as therein a high compression is transformed into an advantage. Besides this the so-called equal pressure processes show, when executed in a .double-.piston engine, the very important advantage, that the total surface of the dead space is smaller than in a single-piston engine, since for the same work volume the diameter of the pistons is smaller on account of the longer stroke, so that the relation between diameter of pistons and their stroke approaches more the ideal proportion 1:1, and besides this, the shape of the dead space is rendered more advantageous. For this reason the losses of heat are reduced during the compression and during the' combustion which takes place at the beginningof the expansion stroke, and all the more so, since theatomized or vaporized fuel, does not so easily come into contact with cold surfaces on account of the favorable position and shape of the combustion chamber, for which reason the starting of the engine is greatly facilitated. The injection of the fuel, according to my present invention, always takes place at the middle between the two inner dead points of the pistons, so that the fuel comes into contact with the fresh air toward both pistons, by which means the complete combustion of the fuel is favored.

As a result of minimizing the cooling off .for large engines.

' To show by way of example how my present invention is put into practice, attention is drawn to the accompanying drawing, wherein Figure 1 is a vertical longitudinal sectional view of an engine operated according to my invention. Fig. 2 is a plan view of said engine. Fig. 3. is a sectional view taken on line 3-3 of Fig. 1. Fig. 4.; is a similar view on line 44 of Fig. 1. Fig. 5 is a diagram which shows at a glance the increase of useful work obtained by this engine as compared with equal pressure engines with but one piston as employed hitherto.

In Figs. 1-4- inclusive 1"is the working cylinder and 2 is the cylinder of the scavenging and charge air pump. 3 indicates the cylinder of the air pump which furnishes the highly compressed air employed for atomizing or vaporizing the liquid fuel. I} is the'front working piston and 5 the rear working piston, whereas 6 'is the piston of the scavenging pump. 7 represents the piston of the atomizing or vaporizing pump. 8 are the inlet openings for the scavenging air in the working cylinder and 9 are the outlet openings for the waste gases. 10 represents the main shaft of the engine, and 11, 12 and 13 are the driving means for operating the fuel pump 14, the fuel valve 15, and the slide valve 16 of the air pump 2. 17 is the eccentric for the operation of the slide 16, and 18 the eccentric'rod which cooperates with the eccentric 17. 19 is the suction valve and 20 the pressure valve of the atomizing or vaporizing pump, whereas, 21 is a pipe which leads from the atomizing or vaporizing pump to the fuel valve 15. The pipe 22 connects the fuel pump 14 with the valve 15 operated by means of the cam 23 and the levers 24, 25, and the rod 26 arranged between the latter. 27 is the crank whichtransmits motion to the fuel pump by means of the connecting rod 28. 29 is the exhaust port and 30 the pipe which connects the slide I box of the air pump 2 with the inlet openings 8 and at the same time performs the duty of a reservoir. 31,-31', 32, 32', are rods for the transmission of motion from the main shaft 10 to the traverse 33, to which the pistons 5, 6, 7 are coupled. The front piston 4 is connected to the main shaft by means of the connecting rod 34 and the piston rod 35.

The operation of the engine is as follows Shortly before the piston 4 has andt reached its outer dead point it uncovers the outlet openings 9 through which the waste gases of the previous working stroke escape. Immediately after this the piston 5 uncovers the inlet openings 8 through which the scavenging and charging air enters from the Pipe or receiver 30 to drivethe remainder tie waste gases out of the cylinder and to refill the working cylinder 1 with fresh air or an equivalent non-combustible gas. During the following outstroke this charging air is so highly compressed, that it reaches a temperature sufficiently high for igniting the employed fuel. When the working pistons 4 and 5 have almost reached their inner dead oints the cam 23 opens the valve lie atomizing air, wl-ich during the previous working stroke was highly compressed in the pipe 21, blows the-fuel forwarded by the fuel pump 14 in a finely atomized or vaporized condition through the opening 36 into the working cylinder 1, wherein it is ignited by the highl compressed charging air and then trans 'ormed into gases. The admission of fuel is continued during a part of the working stroke (up to 10-12 per cent. of the stroke when the compression is driven to to 33 atmospheres) in such a manner, that the resulting change in the rise of temperature in connection with the increase of the volume does not result in a substantialchange in the pressure. After the fuel valve has been closed, the expansion of the hot gases takes place, until near the close of the working stroke the working piston 4 uncovers the outlet openings 9 again, whereupon the scavenging of the cylinder 1 begins anew. This shows, that the engine works according to the so-called equal pressure process. Fig. 5 represents a diagram of this ngine in comparison with a diagram of a single piston equal pressure engine, in which diagram a represents the expansion curve of the new double-piston engine and b the expansion curve of the single-piston engine. he difference which exists between these two expansion curves is based upon the proportions of the cylinder surfaces of these two engines.

It is a well known fact that the transmission of heat under otherwise the same conditions is proportional to the area of the cooling surface. In a double-piston engine there is at the inner dead point position and during the first art of the out stroke a considerably smal er cooling surface present than in a single-piston engine for an equally large inclosed volume of air or a mixture of gases. During the latter art of the out stroke this proportion will 0 course, turn in favor of the single-piston engine. As however, this favorable influence at the beginning of the stroke of the'double-piston engine redominates considerably and besides this t e loss of a heat unit at the close of the stroke does not by any means amount to such a loss as when one gets lost at the beginning of the stroke, because in the latter instance the whole work of expansion '5 would get lost, the diagram of'the doublepiston engine is the better one. For the compression curve the double-piston engine is likewise advantageous, since by the equally strong compression a higher temperature is obtained, which in turn assures a better ignition and a completer combustion of the fuel employed. Besides this a higher temperature facilitates the starting of the engine and the combustion of difiicultly ignitible fuel is made possible.

What I claim is:

The method of operating two-cycle slow combustion engines, which consists in compressing the air from two opposite directions simultaneously until it reaches a temperature higher than the igniting point of the fuel employed, injecting into said air when almost compressed to its smallest volume a quantit of fuel in a finely divided condition, whereby the fuel is immediately ignited by the heat of the air, continuing the injection of the fuel during a part of the working stroke, ex anding the resulting gases in opposite di ections simultaneously and driving out the waste gases by a straight continuous air stream entering the workingcylinder at one end and leaving it at the opposite end.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses HUGO JUNKERS.

Witnesses:

HENRY QUADFLIEG, ELISE KALBUSCH. 

